The present invention relates to automatic filling machines wherein empty cartons are conveyed along a path while being filled with liquid and sealed, and more particularly to liquid dispensing units for such machines.
High speed automatic filling machines such as is disclosed in U.S. Pat. No. 4,448,008, have been used for filling cartons with liquids, such as milk and juices. These filling machines are required to dispense a predetermined quantity of liquid in each carton as it advances through the filling section of the machine.
One type of dispensing unit that has been used is a double bellows type apparatus such as that disclosed in U.S. Pat. No. 4,402,461. This patent discloses a dispensing unit having a pair of bellows interconnected by a sleeve containing a spring-biased check valve that controls the flow of fluid from the upper bellows to the lower bellows. A fixed discharge nozzle is mounted at the lower end of the lower bellows, and a movable discharge valve element is biased toward a closed position by a spring. The sleeve is mounted for reciprocating movement in an axial direction toward and away from the fixed nozzle. The end of each bellows that is connected with the sleeve moves with it. The opposite ends of the respective bellows are held stationary, so that the axial movement of the sleeve toward the nozzle compresses the lower bellows and expands the upper bellows.
An actuator raises the sleeve vertically to contract the upper bellows while simultaneously expanding the lower bellows. This action opens the check valve in the sleeve and allows liquid to flow from the upper bellows into the lower bellows. The check valve closes when the movement of the sleeve stops. The actuator then lowers the sleeve to expand the upper bellows while simultaneously contracting the lower bellows. The increase in pressure in the lower bellows overcomes the spring force on the discharge valve element, thereby causing the valve to open, and the liquid present in the lower bellows flows into a carton. The sequence is then repeated transferring liquid sequentially from a supply source into the upper bellows, then into the lower bellows, and finally into the individual cartons.
Since these dispensing units are primarily used for liquid food products, such as milk, or other dairy products, the filling process must be carried out under aseptic, or hygienic conditions. There must be no opportunity for contamination to occur during the filling operation. The units must be designed to prevent bacteria from entering the carton or the filling nozzle during the filling process, since this would cause the bacteria to enter the liquid food product and to be packaged in the carton with the product.
In prior filling systems, it has been found that there is a tendency when filling cartons with milk, for example, that the liquid flow pattern generates foam on top of the liquid contents in the carton. The presence of foam interferes with the closing and sealing of the carton. The presence of foam also is a limiting factor in attempting to increase the rate of filling of the cartons. The presence of foam may lead to unhygienic filling conditions. Attempts have been made to reduce the amount of foam that is present during the filling operation. For example, U.S. Pat. No. 4,375,145 discloses in FIG. 10 apparatus for filling a carton in a manner that the generation of foam is minimized. U.S. Pat. No. 4,448,008 discloses the use of tubes to draw off any foam that may be present (Col. 8, lines 11-16).